Distillers syrup is a solution or suspension of corn protein and corn oil in water which can be dried to obtain an animal feed product. Distillers syrup is often blended with distillers grains and dried in a rotary steam tubed dryer. A disadvantage of this method is the limit of about 50% dried syrup in the blended product of the dried distillers grains and the dried syrup or DDGS. Additional syrup applications cause the solids to adhere to the surfaces of the dryer. Another disadvantage of the conventional method is the high capital cost.
Alternatively, distillers syrup may be dried using a rotary drum dryer. Careful control is required to avoid overheating the product with a loss of protein content. Further, these driers require high capital cost.
Solutions and suspensions of organic solids in water may also be dried using either a fixed bed dryer or a rotating bed dryer. Representative patents directed to such process and apparatus are U.S. Pat. Nos. 3,309,782 to Ellis: 3,416,239 to Louks. and 4,217,701 to Mathews.
Ellis discloses a method and apparatus for drying grain in which the grain is loaded on a perforated floor of a cylindrical container with the grain spread to form a layer of a certain depth having a concave contour to the upper surface of the layer. Heated air is forced upwardly through the perforated floor and layer of grain, and the grain is removed when it is dried to a predetermined average moisture content.
Louks treats granular material in a cylindrical storage bin having a lower floor and an upper perforated floor forming upper and lower compartments. A sweep auger is movably mounted on top of the perforated upper floor for moving granular material therein to apertures permitting the granular material in the upper floor to be dumped from the upper compartment into the lower compartment. An evacuating conveyor is provided within the lower compartment including an auger mounted below the lower floor for removing material and a second sweep auger movably mounted on the lower floor for moving granular material on that lower floor to the evacuating auger. Heated air is supplied below the upper floor for perculation through the granular material within the upper compartment.
Mathews discloses a bin grain dryer similar in some respects to that of Louks, but utilizes a perforated lower floor and a perforated upper floor. The first perforated floor carries a substantial column of moist grain which is subjected to the passage of hot air moving upwardly through the perforations for drying the grain. An auger sweep arranged within the upper chamber removes portions of the grain lying closest to the surface of the perforated upper floor and discharges that grain downwardly through a passageway in the first floor for distribution uniformly over a substantial column of grain carried on the second floor. The second floor has cooling air passed through its perforations. An auger sweep arranged to remove portions of the grain closest to the surface of the perforated lower floor, discharges that grain downwardly through a central passageway for deposit on a radially disposed conveyor in a bin below the second perforated floor to deliver the grain radially out of the cylindrical bin.
While the apparatus of the three patents described above facilitates the drying of granular material, particularly grain, and while such apparatus incorporates elements necessary to the practice of the method and apparatus of the present invention, such apparatus is not cognizant of the problem of the limitation of blending distillers syrup with distillers grains and drying of the same in a rotating or fixed bed dryer to enable a significant increase in the percent of dried syrup in the blended product of dried distiller grains and dried syrup, DDGS.
It is therefore a primary object of the present invention to provide an improved fixed or rotating bed dryer to enable drying distillers syrup or like solutions or suspensions of organic solids in water or other liquid to obtain granular solids, and the method of achieving the same in which the dried distillers syrup content may be significantly increased, the cost of the apparatus and process kept relatively low, where dust emissions are eliminated, and the process and apparatus is easily controlled.